1. Field of the Invention
The present invention relates to a leakage detector for detecting occurrence and positions of leakage of a fluid such as water or gas flowing a fluid conduit such as a water pipe or a gas pipe buried under the ground.
2. Description of Related Art
As a detector for detecting occurrence and positions of leakage of a fluid such as water or gas flowing a fluid conduit such as a water pipe line or a gas pipe line buried under the ground, there has been known an audible leakage detector 81 comprising a vibration detector 82 having a pickup 83 and a cord 84, a voltage amplifier 85, and a headphone 86 as shown in FIG. 8 (Refer to, for instance, Japanese Patent Laid-Open Publication No. HEI 10-325778).
When occurrence and a position of leakage of water in a water pipe line is detected with the leakage detector 81, an operator holds the voltage amplifier 85 hung down from the operator's neck portion with a belt on the operator's wrist with the belt, and also mounts the headphone 86 on the operator's head as shown in FIG. 9. In this state, the operator places the pickup 83 on the ground surface holding the cord 84 with one hand at an appropriate position.
When power for the voltage amplifier 85 is turned ON, water leakage sounds caused by minute vibrations generated at a water leakage point in a water pipe line and propagated through the earth are caught with the pickup 83 placed on the ground surface, and are converted to electric signals. Then the electric signals are voltage-amplified by the voltage amplifier 85 to an audible level, and the sounds are output from the headphone 86 in the audible state.
The operator places the pickup 83 on the ground surface along the water pipe line with a space of 0.5 to 1.0 m and listens to the output sounds from the headphone 86. Then the operator determined according to amplitude or tone of the output sounds whether water leakage has occurred or not, and determined, when a level of the output sound is maximized, that the water leakage point is present in the water pipe line just below.
The vibrations (sounds) generated at the water leakage point in the water pipe line are substantially attenuated while propagating through the ground before reaching the ground surface, and change to minute vibrations. Therefore, the works for detecting water leakage are generally performed at night when traffic noises generated by cars, pedestrians, and the like, industrial noises from factories and construction sites, and dairy life noises generated by in-store equipment, automatic vending machines, and the like become extremely small.
Even at night, however, actually the traffic noises by cars, pedestrians, and the like are temporally generated, and also dairy life noises by in-store equipment installed in store staying open until late at night and automatic vending machines are constantly generated, although the nose level is low. In the situation as described above, when noise detection is performed with the leakage detector 81 based on the conventional technology, the noises are captured by the pickup 83 and mixed in output sounds from the headphone 86, and therefore it has been difficult to accurately detect occurrence and positions of leakages without fail.
Furthermore, in the leakage detection work with the leakage detector 81 based on the conventional technology, an operator listens to output sounds from the headphone 86, determines occurrence of leakage according to amplitude and tone of the output sounds, and detects a leakage point when a level of the output sounds is maximized, and therefore the work can be performed only by those substantially experienced and skilled in the leakage detection work.